1. Field of the Invention
The present invention relates to spheroidal alumina particulates having bifold porosity, to the preparation of such particulates, and the use thereof as catalyst supports or carriers.
2. Description of the Prior Art
It is known to this art, e.g., from French Pat. No. 1,503,495 to prepare spheroidal alumina particles by forming according to the so-called "oil drop" or "drop coagulation" method, followed by aging, drying and calcining, from a mixture specifically comprising a boehmite sol and amorphous alumina, calcined alumina (in gamma form) and a pore-forming agent (starch and/or carbon black).
This process has numerous disadvantages: the boehmite sol and the amorphous alumina are prepared from metallic aluminum by a very expensive and complex process; furthermore, in order to obtain lightweight materials, pore-forming agents must be included. Also, it is absolutely required according to such process to effect a ripening (or aging) of the spheroidal particles in ammonia, after shaping, to obtain truly solid products. Cf. French Pat. Nos. 2,179,967, 2,185,444, 2,215,389 and 2,245,408; U.S. Pat. No. 2,492,167; German Pat. No. 1,032,728.